ENH: initialising `MultiIndex` with a `dtypes` param

[attack68]

Feature Type

• Adding new functionality to pandas

• Changing existing functionality in pandas

• Removing existing functionality in pandas

Problem Description

See #54521 for the motivating example.

We can currently set the dtype on an Index but there is no dtypes argument for a MultiIndex.from_tuples.
Perhaps it is enough to document how to achieve the equivalent of from_tuples by using from_arrays where the arrays are Index with a dtype set.

Feature Description

.

Alternative Solutions

.

Additional Context

.

[chaoyihu]

Thanks for proposing the workaround! It works for a user case mentioned in issue 59003. I will open a PR to document it.

Despite the workaround, I think initializing MultiIndex with a dtypes param should still be supported. Currently the MultiIndex constructor has a dtype parameter in its function signature, but the parameter is never accessed in the function logic. To me this seems to indicate that initializing with a dtypes param is intended, just waiting to be implemented.

The helper functions including from_arrays(), from_tuples(), from_product(), and from_frame() rely on the MultiIndex
class constructor, thus they do not take parameter for dtypes. Once relevant logic is added to the class constructor, the helper functions can also be updated.